What Size Is a Battery Terminal? Car, Marine Terminal Sizes

Car mechanics can be quite challenging. Just when you think you have a handle on parts and sizes, the car manufacturing companies throw you a curveball. The battery terminals are not all the same size. The size you get depends on the car brand.

What size is a battery terminal? For most cars, the standard battery terminal size is between 11 and 13 mm, those sizes equal to just under 1/2 inch to just over 1/2 inch. For marine batteries, the positives are usually 3/8ths and the negative is only 5/16ths.

To learn more about the different car battery terminal sizes just continue to read our article. It has the information you want to know about so that you can buy the right size cables for your battery. The differences are minute though.

Are Battery Posts Different Sizes?


The best answer that can be given is that they can be. While there is supposed to be a standard battery post size for most batteries, this is not always the case. Different battery makers place different sized battery terminals on their products depending on the specs given by the automaker.

Most car battery terminals will be in the 11 to 13 mm range which really is not a very large difference. But it is enough to make a difference when you try to tighten the battery cables. They may not tighten because the terminals are too small.

Other car battery terminal sizes can be found in the 8, 10, and 11 mm sizes with 12 and 13 thrown in for good measure. If you want to see how those measurements convert to imperial sizes, click on this link to get to a handy chart.

Does Ring Terminal Size Matter?

Yes, it will as there is no one size fits all ring terminal size. Each ring terminal is made for a specific-sized stud. That means that if your stud size is 1/4” then you will need a 1/4” ring terminal.

If you are not sure of the size of the ring or the stud, just take the old one into the hop or hardware store with you and match them up. Even if the smaller ring terminal is cheaper, it does no good to buy it. it won’t fit.

Or if you go larger, there is no way to shrink that ring terminal down to the right size. To help you find the right ring terminal for your vehicle or boat, here is a handy chart that should clear up matters.

Sometimes the ring terminals are color-coded so you can match colors and still get the right one without knowing the size.

What Size Are Battery Terminal Bolts?


Generally, these bolts only come listed in metric sizes. On one brand of battery, the M8 or 8mm bolt size is used as the standard size. But that is not the only figure you will need to know.

To correctly identify this bolt you would need to know the full equation which is M8 x 1.25 x 12 mm. The M stands for metric, the 8 is in mm and is the nominal diameter of the bolt and the 1.25 is the pitch of the threads in mm. Finally, the 12 stands for the length of the bolt.

The difference between the bolt measurement and the terminal measurement is that the 12m in the M8 x 1.25 x 12mm is the depth of the terminal opening. For one brand of battery, here is a chart to help you understand what we are talking about.

Different brands will have different charts.

What Size is A Standard Car Battery Terminal?

This will depend on the auto maker’s specs. Usually, the different brands of cars will have their own specs they want the battery maker to follow. Those sizes are not always the same between brands.

For example, the usual or normal standard size of a car battery terminal is between 11 and 13 mms or around 1/2 inch. But Nissan goes for the 10mm size and in its top posts that measurement is usually 1/2 inch or 9/16ths.

The best thing for you to do is check your service manual to see the actual size of the battery terminal on your brand of car. You can get some terminals as small as 8mm or 9 mm depending on the size of car you bought.

Keep in mind that the battery terminals are not the same size either. usually, the positive terminal is larger than the negative one. What that tells you is that you have to buy 2 different sizes of clamps to make sure you get a good connection.

Marine Battery Terminal Stud Size


Marine batteries may be a bit more standard than car batteries but you never. They do imitate the car battery by having two different sized terminals on the battery itself. The positive terminal comes in at 3/8ths of an inch while the negative comes in at 5/16ths of an inch.

The unique feature of many of the marine battery’s terminals is that they come with a 3/8ths inch stud that uses a wing nut to make the proper connection. This wing nut design is said to be faster and easier to use than normal battery terminal designs.

You also may find that many of these terminals come in 5/16ths of an inch size for both the positive and negative terminals. That tells you that some standardizing of size may be taking place in the marine battery industry.

Measure your terminals to make sure and then simply shop for the same size. That way you won’t go wrong.

Motorcycle Battery Ring Terminal Size

This option is going to be a little bit smaller than the car or marine battery ring sizes. Some of the rings are advertised at 6.4 mm or .250. They will need to be crimped and you will need a strong crimping tool to do that task.

These rings are made for wires measuring 8 to 10 AWG and they come with a 1/4 inch hole. Ring terminals will work for both top and side-mounted battery terminals and you can get them in different construction materials.

The type of ring you do get will depend on the type of battery you have in your motorcycle. Different batteries have different requirements and you should check this chart out to see if you have the right ones or not.

Battery Lug Size Chart


It is a little difficult to place a chart here as there are so many different lugs and lug sizes to deal with. There are also different shapes to contend with and not every car, boat, or motorcycle uses the same shapes.

Plus, there are different construction materials used to create these lugs. The best thing to do is to link to several charts already created to help you find the best lug that you need for your vehicle, boat, or motorcycle.

The first chart is at this link and it helps you find the right-sized wires to attach to the lug. The second chart is at this link, and it is a very comprehensive set of charts that make sure you get what you need.

The third chart, at this link, is added just in case we missed anything. These very detailed charts should make sure that you have the correct information

Battery Screw Terminal Size


These are all supposed to be standard size and the best way to get the right one for your vehicle is to remove it from its spot and go to an auto parts store to match it up. Sometimes they are referred to as bolts which may cause some confusion.

One size you can expect to need would be the 3/8th inch and it may be about 1 1/8 inches long. You might find a 5 by 9 mm screw and those will be for cars made under the metric system.

There is also the 12mm that is 1 1/4 inches long and those numbers are just to get you started on the right path. The length and size of the screw your car will need will depend on the make, model, and brand of the vehicle.

Rarely will you find a one size fits all screw for battery terminals.

Some Final Words

The most important piece of information you need is that battery terminals, bolts, and other key parts are not all the same size. Many vehicles will have the same size but you may be the exception to the rule.

When in doubt, go to your auto parts store or trusted mechanic and ask them. They will have what you need in stock and should be able to fit your battery with new parts very easily.

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